设计模式-装饰模式之重新理解

装饰模式：动态地将责任或者功能添加到对象上，是对象又增加了除去本身外的其他功能。

在设计过程中，大家都知道一些基本的原则，比如多用组合少用继承。但是装饰模式就是使用到的继承。装饰者和被装饰的对象必须是一样的类型，也就是有共同的基类。这是关键的地方，装饰者是对被装饰者的扩展装饰而来的，装饰者本身和被装饰者属于同一种类型，它们具有相同的接口，装饰者能够替代被装饰者。

示例：
定义飞机类

#pragma once

//飞机基类

class AirPlane {
public:
	AirPlane();
	~AirPlane();

	virtual void fly();
};

#include "AirPlane.h"
#include <stdio.h>

AirPlane::AirPlane() {
}

AirPlane::~AirPlane() {
}

void AirPlane::fly() {
	printf("飞机在飞！！！\n");
}

#pragma once
#include "AirPlane.h"

//带有绘图的飞机

class DrawPalne :public AirPlane {
public:
	DrawPalne(AirPlane* airPlane);
	~DrawPalne();
	virtual void fly()override;

private:
	AirPlane* _airPlane = nullptr;
};

#include "DrawPalne.h"
#include <stdio.h>

DrawPalne::DrawPalne(AirPlane* airPlane) {
	_airPlane = airPlane;
}

DrawPalne::~DrawPalne() {
}

void DrawPalne::fly() {
	printf("带有绘图的");
	_airPlane->fly();
}

#pragma once
#include "AirPlane.h"

//带有导弹的飞机

class MissilePlane :public AirPlane {
public:
	MissilePlane(AirPlane* airPlane);
	~MissilePlane();
	virtual void fly()override;
private:
	AirPlane* _airPlane = nullptr;
};

#include "MissilePlane.h"
#include <stdio.h>

MissilePlane::MissilePlane(AirPlane* airPlane) {
	_airPlane = airPlane;
}

MissilePlane::~MissilePlane() {
}

void MissilePlane::fly() {
	printf("带有导弹的");
	_airPlane->fly();
}

#pragma once
#include "AirPlane.h"

//带有雷达的飞机

class RaddarPlane :public AirPlane {
public:
	RaddarPlane(AirPlane* airPlane);
	~RaddarPlane();

	virtual void fly()override;
private:
	AirPlane* _airPlane = nullptr;
};

#include "RaddarPlane.h"
#include <stdio.h>

RaddarPlane::RaddarPlane(AirPlane* airPlane) {
	_airPlane = airPlane;
}


RaddarPlane::~RaddarPlane() {
}

void RaddarPlane::fly() {
	printf("带有雷达的");
	_airPlane->fly();
}

使用过程：

#include <stdio.h>
#include "AirPlane.h"
#include "DrawPalne.h"
#include "RaddarPlane.h"
#include "MissilePlane.h"

int main() {
	AirPlane* plane = new AirPlane;
	plane->fly();

	//装饰上可以绘图的飞机
	plane = new DrawPalne(plane);
	plane->fly();

	//装饰上可以带导弹的飞机
	plane = new MissilePlane(plane);
	plane->fly();

	//装饰上可以带雷达的飞机
	plane = new RaddarPlane(plane);
	plane->fly();

	return 0;
}

运行结果：

aaa